I'm looking to build a set of board formed tiered retaining walls in my front yard (pictured below for a general idea, colored for reference). I've done a bit of research for how to go about this. Curious of folks thoughts on the project or any concerns. I'm located in Denver, CO if that matters. I know it's a lot to read, if you have the time I appreciate the feedback. Thanks!

Dimensions: All walls are 8" thick (I could be talked into 6"). The single larger wall (blue) will have a form totaling 20" in height. 4" of the formed wall should sit below grade when backfilled, followed by the footer. This wall left to right is 18'. The turn back is 40". The other two lower walls (red and yellow) will have forms totaling 10" in height. 3" of the formed wall should sit below grade when backfilled, followed by the footer.

Form: I've seen a couple different tactics for this. 1) Here they're forming with dimensional lumber. Notably using stakes into the ground on the outside of the form to "hold" the bottom width and temporary wooden spreaders at the top (lightly tensioned with rebar tie wire) to "hold" the top width. The wooden spreaders are removed during the pour leaving the tire wide to prevent the form from widening. 2) Here they're forming with plywood leveraging snap ties (albeit a ~6' wall and not a low lying wall). This method seems easier, but at the cost of snap ties and a good amount of 2x4 lumber. However, this method I feel would produce a more consistent and clean finish \ texture on the wall.

Concrete: I'm planning on using 4000PSI concrete with nothing less than a 4" slump. It's my understanding the slump is something I'll have to roughly test for when my ready mix arrives. I don't want the concrete too fluid as it will simply flow out the bottom of the form. As far as yardage is concerned (only accounting for the two walls on the left side of the home, blue & red), the volume comes to 1.3 yards³. This does not take into account the footer which raises a question. How large should the footer be, should it extend 4" below the wall and outwards front and back 2"? I have two options for concrete supply, a single 2 yard³ option or a larger truck which can delivery anything from a short load upwards to 8 yards³. That said, if I can get away with the 2 yard³ option that would be ideal.

Rebar: Likely going to use 3/8" rebar. All walls, will have two horizontal runs of rebar overlapped no less than 5'. I'm still working through the rebar install logistics, might suspend them during the pour or elevate them off the ground with some supports (tbd).

Drainage: I plan to put 3/4 PVC weep holes in the larger (blue) wall. These will be placed every 4' and will sit 4" below the backfill. I still need to research how these are integrated into the form and what prevents them from just clogging with dirt and mud when it rains. Even with the weep holes I'm a bit concerned with building a wall so close to the foundation of the house. I was thinking of crushed rock behind the larger (blue) wall and installing perforated pipe allowing excess water to drain to the left and back (the rock would be graded that direction). I'd do something similar on the smaller (yellow) wall on the right (allowing water to exit to the right).

 

Id scrap all the wood and go with a concrete product, dimensions wall blocks or some type of retaining wall material, wood just isn't that durable for that kind of application and even if treated it will eventually rot.

Dig a 6-8" footer, fill and tamp with crushed limestone.

What your showing is a very small, low bed, so something that low doesn't even need any type of drainage

 

The walls are not made of wood, they would be poured concrete. The only wood is for the forms. I can see how that was not clear, hopefully this helps. Thanks!

 

Yep, so I'd still look at retaining wall or dimensional wall stone for the material, your going through a LOT of work for curbs that are of minimal height.

 

On your first link, there is no footer. No need for a footer actually. All they did was dug a trench, formed it, and then poured the concrete. Wood is used as form most of the time. No need for a concrete truck. This is a very small wall. If i were you, i'd buy some prepackaged concrete mix at homedepot. Mix and pour it myself. I am doing something similar in my back yard but not with concrete. With a concrete wall like that, you'd have to stick some "fake" bricks or stones. Otherwise, it wouldn't look at good.

No need for rebar. That's an over kill. But if you insist, i'd use thin wires like this. Thin wires will not hurt the concrete. Good luck.
https://www.homedepot.com/p/42-in-x-...0570/309328840

 

Marq1 I hear you on it being a lot of work, it definitely is for the look I'm after. I did consider the stackable retaining wall blocks, however, it's just not the look I am after. yes, the lower wall is pretty close to curb height. I'll think through whether or not I keep them. Thanks for the feedback on the drainage!

 

NHOwner
Perhaps I described it wrong, I agreed it's not a traditional footer. I meant somewhat of a wider base. In the first link it's mentioned the concrete "mushrooms out the bottom" as the forms don't go clear to the ground. I appreciate the feedback and will back off my original idea of having a substantial wider base under what is formed.

I calculated the volume of the two left walls and it's around 1.3 yards³, that's a lot to mix and pour (~80 60 lb bags). Two yards of ready-mix delivered in my area is $480. I'd rather pay ~$200 more for a ready mix delivery than 2 pallets of 60 lb bags.

I hear you on the stone veneer, I considered it. There's a raw concrete look I'm after. Below is an example.

I'll check out the then wire, thanks for the feedback.




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Ok, i see what you mean. Rule of thumb for footers is twice the width of the thickness of the wall. So if the wall width is 6 inches, footer should be 12. So that's 3 inches front and 3 inches back of the wall. Would having a footer hurt? No. It's your money and your property. If it makes you sleep better at night, then you need to get it. Good luck.